Lightweight, portable, vibrating, concrete screeds of the type to which the present invention is related are described in applicant's prior U.S. Pat. Nos. 4,030,873; 4,213,749; and 4,253,778. The general state of the art with respect to such type vibrating concrete screeds is believed to be fully set forth in these references and therefore will not be restated.
As another aspect of the prior art as taught in U.S. Pat. Nos. 3,224,348 and 3,377,933, it has been previously known to provide a screeding apparatus which is also adapted to form curbs on the sides of the slab being screeded. However, it will be noted that the prior art apparatus represents an extremely heavy and relatively complex and therefore relatively expensive type of apparatus. Pouring of concrete roadways is most often seasonal and breakdowns to such complicated machinery are costly in time and labor to contractors attempting to meet job time schedules. Small contractors are most often unable to afford such large machinery for finishing concrete roadways even on a rental basis.
U.S. Pat. No. 3,412,658 is also of interest to the present invention as teaching a relatively simplified road surfacing and single curb-forming device. Also, the screed of this patent utilizes a vibrating shaft to impart vibrations to the screed and also utilizes a motor-driven winching apparatus. However, the screed of this patent is not illustrated as being adapted to form a pair of curbs simultaneously nor does the patent teach the concept of combining the curb forming and winch apparatus in a detachable structure as with the present invention.
U.S. Pat. Nos. 3,472,134; 3,600,773; 3,799,714; and 4,027,990 are further illustrative of small curb gutter and/or sidewalk forming devices. U.S. Pat. No. 4,027,990 is also noted as having a trailing skirt or apron for smoothing the formed curb. So far as can be determined, the described skirt is made of formed sheet metal and therefore would be expected to impart undesirable vibrations to the top surface of the formed curb.
As a general observation, it is believed that the introduction of the screed shown in applicant's copending application Ser. No. 251,970 represents the first commercially available lightweight, portable, vibrating-type concrete screed having the ability to screed an entire roadway simultaneously with forming curbing and guttering on both sides of the roadway and the ability to form crown and valley type formations in the roadway contour. As another observation, it can be said that in those screeds having the ability to form a curb, the customary practice has been to install a vibrator in the hopper throat to vibrate concrete being fed through the hopper to form the curb. The prior art patents will also be noted as teaching the practice of vibrating the hopper structure itself. Further, in those instances where the screed has been provided with a smoothing skirt to smooth the formed curb, no provision has been made to both vibrate the concrete in front of the hopper and also dampen the vibrations imparted to the smoothing skirt so as to both improve curb-forming and smoothing to minimize the amount of follow-up smoothing and touch-up work which is typically required in any screeding and curb-forming operation.
With the foregoing discussion of the prior art in mind, the present invention seeks to provide a still further improved lightweight, portable, vibrating-type concrete screed having the ability to screed an entire roadway simultaneously with forming curbing and guttering on both sides of the roadway. More specifically, the present invention provides an improved apparatus and method for vibrating the concrete immediately in front of the hopper in the direction of screeding, a means for smoothing and dampening vibrations imparted to the formed curb and an improved winching apparatus which can be used independently of the curb-forming apparatus or in conjunction with the curb-forming apparatus. Finally, the present invention seeks to improve upon the screed apparatus disclosed in applicant's copending application Ser. No. 251,970 by utilizing the base unit vibrating shaft as a source of power for operating the winch as well as a probe-type vibrator for vibrating the concrete immediately in front of the hopper. Other objects will become apparent as the description proceeds.